The present invention generally relates to electrophotography, and more particularly, to an electrostatic latent image developing apparatus used for developing electrostatic latent images formed on the surface of an electrostatic latent image support member in an electrophographic process and the like.
Generally, as the electrostatic latent image developing apparatus of this kind, there has conventionally been proposed an arrangement which is adapted to transport the developing material supported, in the form of a magnetic brush, on the outer peripheral surface of a developing sleeve, in a circumferential direction of said sleeve so as to develop the electrostatic latent image formed on the electrostatic latent image support member by causing the developing material to rub against the surface of said support member at a developing region where said developing sleeve and said electrostatic latent image support member confront each other. In the above arrangement, the developing material is to be supplied to the rear side of the developing sleeve with respect to the developing region thereof, and before the above time for supplying, it is required that the developing material (normally composed of a mixture of carrier and toner) has been fully mixed and stirred, with toner particles therein being sufficiently triboelectrically charged.
Accordingly, in order to fully mix and stir the developing material, it is conceived, as disclosed, for example, in FIGS. 6 and 7 of Japanese Patent Publication Tokkosho No. 56-11149, to open opposite ends of a partition wall for neighboring feeding passages, with a developing material stirring and feeding member such as a sleeve and the like incorporated with a magnet roller being disposed in each feeding passage so as to transport the developing material in directions opposite to each other, thereby to circulate the developing material through the two feeding passages based on the rotation of said members.
In the known developing material stirring and circulating mechanism as described above, however, the two feeding passages and the developing material stirring and feeding members are disposed in parallel relation to each other, and since end portions of the respective feeding passages in the feeding direction are closed to be stopped, the developing material in the state as it is collected or stagnant at these closed end portions and is laterally moved when pushed by the developing material subsequently fed thereto, thus flowing into the neighboring feeding passage through the openings formed in the partition wall. In other words, the developing material tends to be excessively large in amount at the downstream side of the feeding direction in each feeding passage, and to be excessively small in amount at the upstream side thereof, and therefore, deviation in the amount of the developing material takes place in the axial direction of the developing sleeve, thus inviting such a problem as uneven development.